1. Field of the Invention
The present invention relates to a sputtering device constituting a part of an apparatus for fabricating a semiconductor device, to eject atoms of a metal onto a semiconductor substrate, and more particularly, to a condensing device for ejecting metal atoms from a metal target onto a semiconductor substrate.
2. Description of the Prior Art
As the degree of semiconductor device integration increases, the dimensions of its contact dimensions are correspondingly reduced while the aspect ratio of the contact is correspondingly increased. In accordance with a semiconductor device employing metal wiring, aluminum alloy is typically used. When forming the metal wiring, aluminum alloy is generally deposited over a substrate using a sputtering process. Adherence of sputtered metal to the substrate, however, is generally regarded to be a limiting factor. Depositing aluminum alloy on the side walls and bottom of contacts formed on the substrate is difficult. This problem becomes more severe as the dimensions of each contact are reduced.
FIG. 1 is a schematic view of a sputtering device employing a conventional condensing device. As shown in FIG. 1, the condensing device, which is denoted by the reference numeral 12, includes a plurality of condensing plates 14 arranged vertically above a substrate 13.
In accordance with a conventional sputtering process, metal atoms are ejected from a metal target 11 disposed directly above a set of condensing plates 14 and then deposited over a substrate 13. Although the condensing plates 14 guide the metal atoms in a vertically downward direction, the metal atoms are generally not deposited in a completely linear manner. Rather, they are deposited in a more or less dispersed manner. This dispersion of metal atoms results from collision of the metal atoms with other metal atoms or with Ar.sup.+ ions of the sputtering gas.
FIG. 2 is a plan view of the conventional condensing device shown in FIG. 1. As shown in FIG. 2, condensing device 12 includes a bundle of condensing tubes each having a regular hexagonal shape constituted by a set of condensing plates 14.
Where a sputtering process is carried out by use of a condensing device 12 having its condensing plates 14 arranged vertically above substrate 13, only the metal atoms exhibiting a substantially vertical orientation are deposited over substrate 13. As a result, a large amount of metal is deposited on the bottom of each contact, as compared to the case where no condensing device 12 is employed. At the side walls of the contact, however, it is difficult to deposit a sufficient thickness of metal to the extent as the thickness of metal deposited on the bottom of the contact. When planarizing both the contact bottom surface and the contact side wall surface, it is desirable that the metal atoms be deposited on the contact side wall surface in an amount similar to that deposited on the contact bottom surface. However, this can not be achieved by the condensing device 12 employed in the above-mentioned conventional sputtering device having its condensing plates 14 arranged vertically above the substrate.